To block applications, you need to configure/install them to the Software Configuration and choose Deny as the disposition policy. This is obviously a nice little chore considering you'll have to maintain these going forward.

To deny installation of third-party applications, you'll need to configure the BES IT Policy options. There's a LOT of documentation on RIM's websites concerning how to do this. Look in their best practices guides for device security. This became a top suggestion for securing devices by RIM when all of those alleged security flaws were discovered, although none ever materialized as an actual threat or issue.

__________________In the beginning the Universe was created. This has made a lot of people very angry and is widely regarded as a bad move.